Flourescent ceiling fixture

[jtfoxman]

Hi all! I have a flourescent ceiling fixture in my kitchen with spots for 4 tubes. I only use the middle 2 spots next to the ballast cover as this gives off enough light. My issue is lately I flick the switch and lights come on but dimly and after about 5-10 sec. they reach there full power. The ends of the tubes are black which means they are starting to go. Should I leave it the way it is until they burn out or change them now? Or could there be another issue? The light buzzes a little bit when turned on, but I believe lots of these types of lights do. I know humidity and cold can due this and it has been extremely humid so far this summer. This occurs in the winter also but alot more buzzing on very cold days.

Thanks for your help.